Vascular disease is the leading cause of death and disability in the world. An estimated 50 million people worldwide suffer from some form of coronary, cerebrovascular and/or peripheral vascular artery disease. Medical technology has advanced dramatically over the years, providing an overall decrease in the cost of care while improving a patient's quality of life. The primary advancement in the treatment of vascular disease has been the advent of catheter-based (or interventional) procedures, which have rapidly gained acceptance--growing from under 325,000 procedures in 1994 to over 1,000,000 in 1997--since they are less invasive and less costly compared to their open surgical counterparts.
Despite the rapid growth in catheter-based procedures, embolic events remain a major clinical problem. Embolic events are typically created by thrombus (blood clot) or plaque which break loose, enter the bloodstream, and become lodged in the artery resulting in the obstruction of blood flow.
Stroke is a form of cardiovascular disease that interrupts blood flow to the brain. A stroke occurs when the carotid artery leading to the brain becomes clogged (ischemic stroke) or bursts (hemorrhagic stroke), preventing oxygen-rich blood from reaching the brain. As a result, brain cells die. Once dead, they do not regenerate which is why damage from a stroke is frequently permanent. Stroke accounts for 10% to 12% of all deaths in industrialized countries. For example, in a population of one million, 1,600 people will have a stroke each year, of which only 55% will survive six months post-stroke, and a third of the survivors will have significant disability. Stroke ranks third in terms of leading causes of death in the United States, behind heart disease and cancer. Strokes cause an estimated 150,000 deaths each year and are the leading cause of long-term disability. Current treatment options include medical management (drug therapy), carotid endarterectomy, or stent-supported carotid angioplasty. Carotid endarterectomy has demonstrated a marked increase in its use during the past two years on the basis of pivotal studies demonstrating a reduction in stroke after carotid revascularization. It is well documented that carotid endarterectomies have a 3% to 6% complication rate, depending if the patient is asymptomatic or symptomatic. Embolization has represented an obstacle to widespread acceptance of stent-supported carotid angioplasty due to the brain's sensitivity to even small amounts of emboli, with clinically significant strokes occurring in the absence of angiographically definable branch vessel occlusions is to compete effectively against the endarterectomy, it must demonstrate equal complication rates. In particular, carotid angioplasty must not lead to an increase in embolization or stroke rates. Industry sources estimate roughly 100,000 carotid endarterectomies were performed in the Unites States alone in 1997. In the same year, approximately 90,000 procedures were performed internationally and these operations are increasing at a faster rate than the United States. The desire among patients to have--and cardiologists to perform--less invasive procedures is evident. Industry estimates indicate that the number of carotid angioplasty procedures in the United states will grow from roughly 3,000 in 1998 to approximately 36,000 procedures in 2002.
The use of an effective emboli capture device or filter could significantly reduce the risk of these often devastating complications, and could potentially become the standard of care--even in low risk cases.
During catheterization of a patient, a guide wire is directed through the patient's blood vessel to the site of interest. For example, the physician may wish to utilize a balloon catheter in order to enlarge a partially obstructed blood vessel at a certain location in the patient's vascular system. To do this, the physician utilizes a guide wire which is directed through the patient's vascular system to the particular site for balloon catheterization. Various medical devices are percutaneously inserted into the patient's blood vessel utilizing the guide wire. The balloon catheter, for example, is mounted at the distal end of an elongated tube. The guide wire is placed in the lumen of the balloon catheter tube such that the balloon catheter can be threaded over the guide wire, through the vascular system and placed at the site of interest by following the guide wire.
In order to enlarge a partially obstructed blood vessel, a physician may use various surgical techniques and biomedical devices or tools including balloon catheters, scrapers or other known medical devices. However, the utilization of these devices sometimes results in a release of an embolus (embolic material) which is an abnormal particle circulating in the blood. In order to reduce complications arising from these medical procedures, physicians sometime utilize filters disposed downstream of the site of interest. As used herein the term "downstream" refers to an item that is spaced a distance apart from a referenced item and in the direction of blood flow through the blood vessel.
U.S. Pat. No. 4,619,246 to Molgaard-Nielsen et al. discloses a collapsible filter basket. The basket includes a woven mesh but does not operate on a guide wire.
U.S. Pat. No. 4,723,549 to Wholey et al. discloses a filter which is expanded based upon inflation of a balloon acting as a donut mounted to expanding frame members of the filter disposed about the guide wire.
U.S. Pat. No. 5,053,008 to Bajaj discloses a filter which is expanded based upon inflation of a tubular balloon.
U.S. Pat. No. 5,108,419 to Reger et al. discloses a filter for capturing particles of plaque which includes a laterally (radially) collapsible bag with a plurality of longitudinally displaced filter cones therein. The bag has a draw string about its mouth which opens and closes the bag both laterally (to deploy or pull-up the conical filters) and longitudinally (to wrap the conical filters and the bag into a small-diameter shape). Each conical filter includes flexible tension supports which carry filter screens or mesh and which open and close based upon the respective longitudinal position of a generally static hub at the end of a guide wire running through the filter basket system. In another embodiment, a single conical filter is utilized with a filter stocking or collapsible bag thereabout. All the tension supports are flexible enough to wrap and twirl within the collapsible bag and wrap the conical filter(s) about the guide wire. Also, a draw string closes the collapsible bag in all embodiments. The flexible tension supports or radial ribs are resilient enough to provide force to spread the conical filter mesh across the lumen of the blood vessel.
U.S. Pat. No. 5,549,626 to Miller et al. discloses a filter deployed from the inside of a hollow tube by axial movement of an inner catheter. The filter is a mesh-like collapsible basket being made of radially expandable materials which can be compressed in the lumen of an outer catheter and radially expand when the basket extends beyond the distal end of the catheter.
U.S. Pat. No. 5,695,519 to Summers et al. discloses a wire, which controllably moves forward and aft, to open and close a generally conical filter by acting on the filter's mouth.
U.S. Pat. No. 5,810,874 to Lefebvre discloses a filter including strips that are radially opened by moving an inboard ring towards an outboard ring. The rings retain forward and aft ends of the strips. The filter can be detached from the guide wire.
U.S. Pat. No. 5,814,064 to Daniel et al. discloses one filter system which utilizes various types of inflatable ribs, tubes or struts and a second filter system wherein the filter material is deployed by longitudinal movement of a push-pull wire relative to a generally static distal end of a tube (see Daniel FIGS. 15-16B). In one embodiment, struts carry filter mesh and are forced radially outward by axial movement of a wire attached to the apex of the conical filter relative to a static tube end. In a collapsed position, the filter is disposed outboard of the static tube. In another embodiment, wire filter mesh has a conical memory shape such that when deployed outboard of a closed end cylinder, a conical filter is created by the memory shaped metallic filter. In another embodiment, only the open end of the conical filter has a memory shape. A further embodiment utilizes memory shaped filter mesh, a cinch wire and a push guide wire.
U.S. Pat. No. 5,911,734 to Tsugita et al. discloses a conical mesh filter with a proximal end strut structure connected to the distal end of a guide wire. Accordingly, the distal end of a guide wire is not downstream of the filter (see Tsugita FIGS. 2-8B). In another embodiment, the filter (conical or concave) is attached to radially outwardly biased struts. In a closed state, the biased struts are retained within a sheath. Upon axial movement of the guide wire relative to the sheath, the struts are moved beyond the sheath, they spring open to expand and deploy the filter. (See Tsugita FIGS. 10-11B). In a further embodiment, an egg beater filter is deployed. One embodiment of the egg beater filter utilizes a compressive spring which pulls fore and aft ends of expandable struts together, thereby radially expanding a filter basket with one side carrying filter mesh thereon. In other words, the filter is spring actuated. (Tsugita FIG. 15A). In another egg beater embodiment, pressure wires "spring" radially outward deploying conical cage wires which retain a mesh filter. (Tsugita FIG. 16). A scroll filter is also disclosed. A further embodiment discloses a filter with an expansion frame apparently made of memory shaped material. Tsugita FIG. 19 discloses a filter with a distally extending inner sheath having filter strut ends attached thereto and an outer sheath having the other filter strut ends attached thereto. To open the filter, the outer sheath is moved distally towards the inner sheath thereby causing the filter struts to buckle radially outward. The struts may be packed densely to form a filter or filter mesh material may be draped over the struts. In a different embodiment, an outer sleeve is longitudinally slitted. (Tsugita FIGS. 23, 23A). When the distal end of the slit outer sleeve is pulled proximally, the slitted region buckles radially outward to provide an egg beater filter. The expanded cage can be draped with filter mesh.
PCT Published Patent Application WO 96/01591 discloses a concave filter deployed by axially shortening the distance between the filter mouth and the filter apex (attached to a distal end of a guide wire). The filter mouth is sprung open by tethers fixed at one end to a static tube. A rod extends through the filter to its apex. The filter opens based upon the relative position of the filter apex on the rod (which extends beyond the apex to form the distal end of the guide wire) and the static tube.